Tag Archives: Rob Sherwood

Can you help Rob identify two mystery signals on the 20 meter band?

I received the following message from my buddy Rob (NC0B) who is trying to identify a couple of signals on the 20 meter band. Rob kindly gave me permission to post his email here on the SWLing Post with the idea that someone may be able to help him solve this:

The following is a description of two odd digital signals observed on 20 meters with transmission modes I do not understand. They may not amateur transmissions, but I have no way to decode them. They stick out like a sore thumb on 20m in the Extra portion of the phone band. The time of day on August 20th was between 11:50 AM and 12:00 PM MDT.

Two weeks ago I was in QSO on 14,170 kHz and occasionally there was the same 10 kHz wide digital signal but centered on 14,171 kHz. It sounded like the old Russian jammers buzz saw modulation. Those signals from decades ago were much wider, and or course we didn’t have high resolution spectrum scopes back then. Today the same transmissions occurred several times, and more than once a minute for about 5 seconds each. In total the transmissions may have occurred on and off for about 10 minutes.

Then after a few 10 kHz transmissions a different signal came on the air a few times with what looked like a digital modulated carrier plus digital sidebands on each side of the middle signal.

Look at the attached JPG file and I’ll try to make sense out of it:

The waterfall image lasts about 50 seconds on the Icom IC-7610 set on slow. There are two different signals to differentiate in this image. The signal I observed two weeks ago and today is 10 kHz wide and today spans from 14,178 to 14,188. It shows up in green on the band scope, and just under it in blue on the water fall for about 3 seconds of the approximate 5 second transmission. You can also see at the bottom of the waterfall the previous transmission that has about 4 seconds worth saved on the waterfall running off the bottom. The horizontal span of the scope was set to 5 kHz per division.

Once the 10 kHz wide signal started, I went to Dual Watch so I could listen for KL7QOW on 14,170 kHz for a sked, and hear the buzzing signal on 14,183 kHz in SSB mode. That frequency placed the carrier position of the SSB 2.8 kHz bandwidth in the center of the 10 kHz wide signal.

Soon after I started observing the relatively flat spectrum of the 10 kHz signal, a new digital signal appeared about 3 kHz lower in frequency. At first it had a much stronger center modulated carrier about 2 kHz wide and then two symmetrical digital signals on each side within about a 6 kHz total bandwidth. I wasn’t able to capture the best picture of the 2nd signal as it appeared to be tuning up. The amplitude difference between the central signal and the separate sidebands initially was about 15 dB. Vertical divisions are 10 dB.

On the waterfall you can see the second type of signal is centered on about 14,180 kHz. The modulation depth of the outer pairs of signals were not constant, possibly due to selective facing. QSB was quite significant at this time at least to Alaska. You can see there was a short break of a few seconds in the 6 kHz wide signal. Every time I have seen the 10 kHz wide signal its amplitude across the transmission bandwidth has been fairly constant, always of short duration, and repeating several times within 10 minutes before terminating.

Does anyone have any idea what either of these transmissions are? I have heard of email digipeaters, but I would not think their bandwidth would be this wide.

Rob, NC0B

SWLing Post community: Please comment if you can help Rob ID these signals!

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Radio Waves: Holme Moss Transmitter, Sherwood Tools, World of LPFMs, Shortwave Revival Response, and Russia “Thrown Back 40 Years”

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Radio Waves: Stories Making Waves in the World of Radio

Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Holme Moss transmitter (BBC Archives)

A look at how the BBC’s third television transmitter in West Yorkshire was built.

These original masts broadcast to the surrounding population until 1985, when they were replaced by a new generation of transmitters.

Originally broadcast 12 October 1951

Click here to watch the video at the BBC Archives.

Sherwood Tools Available (K4FMH Blog)

The work that Rob Sherwood NC0B has contributed to the public over the past decade is unique and an amazing service to hams worldwide. I’m talking about, of course, his summary Table of receive bench tests published at this Sherwood Engineering website. He is independent so no one can think that advertising dollars could skew his assessments or how he presents them. As a CW contest operator, he is very clear that he sorts his table on the basis of what his experience and training has shown him to be the single most important measurement in his table: the narrow dynamic range.

I am not a CW operator or accomplished contester (lol) but enjoy the latter with my small team of fellow hams. But I am a statistician who likes to focus on problems where analytic tools can help foster a wider understanding of the data surrounding the problem area. So, working with Rob NC0B, I’ve created a set of “Sherwood Tools” to visualize his data as well as link them to a couple of other critical aspects of a rig purchase: market-entry price, consumer satisfaction, and the year the radio entered the market. These four vectors of data drive all of these tools, now available over at foxmikehotel.com.

The tools include a sortable Sherwood list where you can sort on any of the nine tests he publishes as well as the composite index of them that I created and included in my two-part NCJ articles in 2021. A set of 3D data visualizations are available to simultaneously view radios on four data elements (that does make it 4D, technically). Several graphs illustrate key aspects of the data, including how to not get tripped-up in the “ranking” of radios where the bench measurements are just not appreciably different. Seeing how the past 50 years of radios appearing in Rob’s Table have made a remarkable and clear progression toward the best receiver performance that modern test equipment can detect is in another tool. In addition, how the trend in getting a receive bang-for-the-buck has progressed over this 50 year period is there, too. Finally, I’ve used the industry-standard tool by Gartner, the Magic Quadrant, to help isolate radios in Rob’s Table that perform and are rated above average at various price points. I call these the Golden Quadrant Lists. Continue reading →

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Rob Sherwood tests the new Yaesu FTDX10

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Many thanks to Rob Sherwood (NC0B) who shares his recent assessment of the new Yaesu FTDX10.

In short: the FTDX10 is now number 3 (at time of posting) on Rob’s receiver test data table— a table sorted by third-order dynamic range narrow spaced. Most impressive!

Click here to download Rob’s full HF test results and his review notes as a PDF.

FYI: I plan to review the FTDX10 this year.

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Rob Sherwood on Ham Talk Live tonight (October 29, 2020)

Rob Sherwood’s presentation: “Transceiver performance for the HF/DX operator”

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Many thanks to SWLing Post contributor, Paul, who shares the following video of a recent presentation by Rob Sherwood (NC0B) for Ham Holiday Oklahoma.

I love Rob’s presentations because not only is he an authority on testing receivers and transceivers, but he also has a very pragmatic approach to operating radios. Rob speaks to the importance of using pre amps, attenuators and adjusting your receiver for band conditions. I’ve been with lifelong ham radio operators and SWLs who never use pre amplification, attenuation, or adjust their RF gain control–these are very powerful tools, especially during the noisy summer months.

If you’ve never seen one of Rob’s presentations before, I highly recommend checking out this one: